It is common practice to use modular (e.g., RJ45) plugs and jacks in combination with twisted pair cabling to interconnect electronic equipment. While the primary purpose of this type of connectivity is to enable the flow of data, it is also possible to use the same medium to transmit limited amounts of power. This is generally referred to as Power over Ethernet (PoE).
PoE allows a single cable to provide both electrical power and data connections, which may eliminate the need for additional power cables and devices such as transformers and AC outlets. Some non-limiting examples of PoE devices include Voice over Internet Protocol (VoIP) phones, wireless access points, network routers, switches, industrial devices (controllers, meters, sensors, etc.), nurse call stations, IP security cameras, televisions, LED lighting fixtures, remote point of sale kiosks, and physical security devices. PoE was launched into the market in 2003, standardized under IEEE 802.3af, and allowed for a power draw of 12.95 W and 350 mA per pair (Type 1). POE+ was launched into the market in 2009, standardized under IEEE 802.3at, and allowed for a power draw of 25.5 W and 600 mA per pair (Type 2). As the need for more and more power becomes apparent, non-standard applications, such as Cisco's Universal Power over Ethernet (UPoE) at 60 W and Power over HDBaseT (100 W), with 1000 mA per pair of current capacity, have arisen. As of 2015 there is a proposal for an IEEE 802.3bt (PoE++) standard with 49 W (Type 3) to 100 W (Type 4) of power draw and 600 mA (Type 3) to 1000 mA (Type 4) per pair of power, and other potential future applications may require a current capacity of 1500 mA per pair or more.
While the earlier-designed connectors could withstand the rigors of the relatively low power required for earlier PoE applications, these connectors lack the design for durability needed to sustain the ever-increasing power demands. One particular issue is the need to reduce damage that occurs to the plug and/or jack during the mating and disconnection.
In a PoE application, upon disconnection (and/or insertion) of the plug and jack connector combination there is an electrical discharge that can damage the plug and jack mating interfaces. This electrical discharge can be an electrical arc (spark) or a corona discharge. A spark is a fast single event that is time independent and may cause a large distinct crater on the plug contacts of the plug, the plug interface contacts (PICs) of the jack, or both. A corona discharge is a relatively slower event that is time dependent, has multiple events, and causes many shallow craters or pits that erode the plug contacts, PICs, or both. These effects are worsened after multiple insertions as erosion caused by mechanical abrasion also damages the plug/jack mating interfaces of both the plug contacts and the PICs. IEC 60603-7 requires a minimum of 750 plug insertions into a jack module. Many vendors test to a higher amount of insertion cycles as for some applications 750 plug insertions is relatively low. The effects of this damage can be seen in the form of physical damage, electrical interface degradation, and, over time, corrosion of the contacts.
Additional constraints on the design are imposed by the need of the connectors to handle a certain amount of bandwidth while at the same time meeting particular parameters such as, for example, near end crosstalk (NEXT), far end crosstalk (FEXT), return loss, and insertion loss requirements. As such, these and other design concerns give rise to the need for robust connectors designed to withstand current and future demands of PoE.